Trafalgar Square Pyramid

A pyramid taller than St Paul's Cathedral dominating Trafalgar Square. It might have happened. These plans from the early 19th century would have marked victories against the French with something a little more ambitious than an admiral on a column.

The image is one of several created by Barratt Homes, showing areas of London as they might have been if history had taken a different turn. Here's another one:

Westminster Airport

The raised landing strip over the Thames at Westminster is inspired by a 1934 suggestion — one of many schemes to bring aircraft into central London from that time. It might have worked for the tiny propeller craft of the time, but the modern jets pictured here would surely plunge into the Thames were they to attempt a take-off.

Regent Street monorail

A ride through central London that avoids traffic jams — this 1960s scheme would have seen monorails carrying passengers along Regent Street at first-floor level. Tradition dictates that whenever monorails are mentioned on the internet, then a link must also be provided to a certain episode of The Simpsons. So here you go.

The Crystal Palace tower

The Crystal Palace was built to house the Great Exhibition of 1851 in Hyde Park. Once the exhibition was over, the great glass building was transferred to Sydenham, and hence the area is today known as Crystal Palace. In an alternative universe, we might call the place Crystal Tower, for one suggestion would have seen the palace rebuilt vertically as shown above. The tower would have stood about the same height as the Shard, more than 150 years earlier, though it's doubtful it could have supported its own weight.

The images above were put together by Barratt London as part of a digital PR exercise that's actually worth sharing. Well done whoever came up with the idea.